Soft drink manufacturers have been facing some challenges in the past month. To begin with, a government panel of nutrition experts recently recommended a tax on sugary drinks and snacks. In a prepared statement released Friday, committee members wrote, “Taxation on higher sugar and sodium-containing foods may encourage consumers to reduce consumption and revenues generated could support health promotion efforts.”

Beyond a potential tax on its products, however, soft drink manufactures were dealt another blow when Consumer Reports published an article warning that those who consume soda daily might develop cancer from exposure to the ingredient that provides many sodas with their “caramel color.”

4-methylimidazole (4-Mel), an ingredient often used to create the brown color in colas and other beverages, could be present in high enough levels to be labeled as a carcinogen. Consumer Reports, in conjunction with the Johns Hopkins Center for a Livable Future (CLF), tested 81 cans and bottles of popular brands of soft drinks from five different manufactures between April and September 2013, and 29 new samples in December 2013.

Perhaps unsurprisingly, the researchers found that different brands of soft drinks contained very different concentrations of 4-Mel. For example, Pepsi One and Malta Goya exceeded 29 micrograms per can or bottle, a dosage above which manufactures are supposed to add a health-warning label as stipulated by California law. And one can of a soda variety had nearly ten times the allowed per day amount of 4-Mel. Coke, Diet Coke and Coke-Zero, however, all had less than 5 micrograms per bottle or can, a level Consumer Reports’ experts determined was “acceptable.”

Interestingly, the authors noted that the second time they tested for 4-Mel, the levels of the chemical were lower in New York samples than before (Pepsi went form 174 micrograms in the first test to 32 micrograms the second time). One of the co-authors suggested that “some manufactures may be taking steps to reduce levels.” Alternatively, it’s also possible that different manufacturing facilities do not carefully monitor the amount of 4-Mel added, which might lead to some variation.

To determine the potential ramifications of their finding, the researchers used data from the National Health and Nutrition Examination Survey to investigate the amount of soda Americans normally consume. The researchers found that over half of Americans between the ages of six to 64 regularly consume soda — often 1 to 2.5 cans each day.

Given their previous findings concerning 4-Mel concentrations in soft drinks, the authors approximate that “between 76 and 5,000 cases of cancer could be caused by 4-Mel in caramel coloring,” and the authors recommended that the chemical be included in future labeling.

Beyond colas, other products such as barbecue sauce, soups, syrup and bread can contain 4-Mel, though 25 percent of American consumption of the chemical is from soda. As Keeve Nachman from the Johns Hopkins Bloomberg School of Public Health said in a prepared statement, “Soft drink consumers are being exposed to an avoidable and unnecessary cancer risk from an ingredient that is being added to these beverages simply for aesthetic purposes.”

One should note, however, that studies of 4-Mel’s potential carcinogenicity has been limited to studies on mice and rats. Specifically, in 2007, the U.S. National Toxicology Program (NTP) accessed the carcinogenicity of 4-Mel in female mice and rats using two-year feeding studies and found “clear evidence of carcinogenic activity” in female and male mice, “equivocal evidence” of carcinogenic activity in female rats and “no evidence” in male rats. Furthermore, no data is currently available concerning the carcinogenicity of 4-Mel in humans and 4-Mel can be naturally formed during the normal processes of roasting foods or fermentation. Given this information, the International Agency for Research on Cancer has classified 4-Mel as “possibly carcinogenic to humans.”

Regardless, if only to provide consumers with information they may find important, the idea of labeling soft drinks is a good one.